There are 12 standard Medigap policies to choose from, with the eye-popping names of A through L. Medigap A is the most basic "core" policy. As you move through the alphabet, the plans add more coverage. For example, Medigap E will offer something that is not included in Medigap D, but will lack a coverage provided in Medicare F.

There is no difference in plans offered by different insurers; plan details are all set by the government. (Important caveat: If you live in Massachusetts, Minnesota or Wisconsin, check with your state insurance company or a private insurer who operates in your state. Medigap policies in these states offer coverage different than the plans followed by the 47 other states.)